SCRAP metal dealers stole jewellery when they went to pick up an old parasol from a woman's home in Quedgeley.
The victim heard the scrap metal collectors in her street and went out to speak to the driver of the Mercedes Sprinter truck.
She asked if he, or one of the other two men in the vehicle, would collect a metal parasol from her and the driver accompanied her through her house into the garden, where he spoke about the services he could provide.
When they came back in, she saw one of the other men walking down her staircase and the third man waiting in the hallway.
The first man tried to block the victim's view and when questioned what they had been doing, he told her she was "imagining everything".
Soon after the men had left, she found various pieces of jewellery had been stolen, including a nine carat gold ring.
The incident happened in Pochard Close between 4pm and 4.30pm on Sunday.
Kim Mowday, crime reduction advisor at Gloucestershire Constabulary, said: "This was an opportunist crime by thieves who showed complete contempt for their victim.
"It's also a salient reminder to be on your guard against burglars who can trick you like this.
"Don't let people into your house unless you know their credentials and are satisfied they are there for a legitimate purpose."
Graham Smith, vice chairman of Quedgeley Parish Council, said the incident was "a bit of a shock".
"There are about three lots of scrap metal dealers going around the area. Of course, you have to have a license now but I'll be warning residents."
The first man is described as white, 5ft 8ins tall, in his 20s and with short dark hair.
Anyone with any information should call 101, quoting incident 353 of April 21.